Summarized Consolidating Financial Data - Consolidating Balance Sheet (Details) - USD ($) $ / shares in Units, $ in Millions	Mar. 31, 2017	Dec. 30, 2016	Mar. 25, 2016	Dec. 25, 2015
Current Assets:
Cash and Cash Equivalents	$ 930	$ 603	$ 731	$ 628
Short-term Investments	287	417
Accounts Receivable - Net	943	938
Receivable from Affiliates	0	0
Materials and Supplies	415	407
Other Current Assets	85	122
Total Current Assets	2,660	2,487
Properties	43,399	43,227
Accumulated Depreciation	(12,140)	(12,077)
Properties - Net	31,259	31,150
Other Long-term Assets	324	318
Total Assets	35,712	35,414
Current Liabilities:
Accounts Payable	898	806
Labor and Fringe Benefits Payable	445	545
Payable to Affiliates	0	0
Casualty, Environmental and Other Reserves	114	115
Current Maturities of Long-term Debt	331	331
Income and Other Taxes Payable	302	129
Other Current Liabilities	187	114
Total Current Liabilities	2,277	2,040
Casualty, Environmental and Other Reserves	252	259
Long-term Debt	10,963	10,962
Deferred Income Taxes - Net	9,648	9,596
Other Long-term Liabilities	903	863
Total Liabilities	24,043	23,720
Shareholders' Equity
Common Stock, $1 Par Value	923	928
Other Capital	170	138
Retained Earnings	11,197	11,253
Accumulated Other Comprehensive Loss	(634)	(640)
Noncontrolling Interest	13	15
Total Shareholders' Equity	11,669	11,694
Total Liabilities and Shareholders' Equity	$ 35,712	$ 35,414
Common stock, par value (in dollars per share)	$ 1	$ 1
Investments in Conrail
Current Assets:
Investment in Affiliates and Other Companies	$ 847	$ 840
Affiliates and Other Companies
Current Assets:
Investment in Affiliates and Other Companies	622	619
Investments in Consolidated Subsidiaries
Current Assets:
Investment in Affiliates and Other Companies	0	0
CSX Corporation
Current Assets:
Cash and Cash Equivalents	648	305	493	444
Short-term Investments	285	415
Accounts Receivable - Net	2	2
Receivable from Affiliates	1,122	1,157
Materials and Supplies	0	0
Other Current Assets	0	0
Total Current Assets	2,057	1,879
Properties	1	1
Accumulated Depreciation	(1)	(1)
Properties - Net	0	0
Other Long-term Assets	2	2
Total Assets	26,454	26,021
Current Liabilities:
Accounts Payable	171	95
Labor and Fringe Benefits Payable	34	40
Payable to Affiliates	3,478	3,457
Casualty, Environmental and Other Reserves	0	0
Current Maturities of Long-term Debt	313	313
Income and Other Taxes Payable	(29)	(346)
Other Current Liabilities	0	0
Total Current Liabilities	3,967	3,559
Casualty, Environmental and Other Reserves	0	0
Long-term Debt	10,206	10,203
Deferred Income Taxes - Net	(207)	(203)
Other Long-term Liabilities	832	783
Total Liabilities	14,798	14,342
Shareholders' Equity
Common Stock, $1 Par Value	923	928
Other Capital	170	138
Retained Earnings	11,197	11,253
Accumulated Other Comprehensive Loss	(634)	(640)
Noncontrolling Interest	0	0
Total Shareholders' Equity	11,656	11,679
Total Liabilities and Shareholders' Equity	26,454	26,021
CSX Corporation | Investments in Conrail
Current Assets:
Investment in Affiliates and Other Companies	0	0
CSX Corporation | Affiliates and Other Companies
Current Assets:
Investment in Affiliates and Other Companies	(39)	(39)
CSX Corporation | Investments in Consolidated Subsidiaries
Current Assets:
Investment in Affiliates and Other Companies	24,434	24,179
CSX Transportation
Current Assets:
Cash and Cash Equivalents	272	281	223	175
Short-term Investments	0	0
Accounts Receivable - Net	198	215
Receivable from Affiliates	2,397	2,351
Materials and Supplies	415	407
Other Current Assets	74	106
Total Current Assets	3,356	3,360
Properties	40,670	40,518
Accumulated Depreciation	(10,662)	(10,634)
Properties - Net	30,008	29,884
Other Long-term Assets	603	607
Total Assets	34,613	34,494
Current Liabilities:
Accounts Payable	698	678
Labor and Fringe Benefits Payable	383	440
Payable to Affiliates	475	500
Casualty, Environmental and Other Reserves	102	102
Current Maturities of Long-term Debt	19	19
Income and Other Taxes Payable	310	459
Other Current Liabilities	178	112
Total Current Liabilities	2,165	2,310
Casualty, Environmental and Other Reserves	203	208
Long-term Debt	757	759
Deferred Income Taxes - Net	9,592	9,541
Other Long-term Liabilities	396	410
Total Liabilities	13,113	13,228
Shareholders' Equity
Common Stock, $1 Par Value	181	181
Other Capital	5,095	5,095
Retained Earnings	16,232	15,994
Accumulated Other Comprehensive Loss	(21)	(19)
Noncontrolling Interest	13	15
Total Shareholders' Equity	21,500	21,266
Total Liabilities and Shareholders' Equity	34,613	34,494
CSX Transportation | Investments in Conrail
Current Assets:
Investment in Affiliates and Other Companies	0	0
CSX Transportation | Affiliates and Other Companies
Current Assets:
Investment in Affiliates and Other Companies	646	643
CSX Transportation | Investments in Consolidated Subsidiaries
Current Assets:
Investment in Affiliates and Other Companies	0	0
Eliminations and Other
Current Assets:
Cash and Cash Equivalents	10	17	$ 15	$ 9
Short-term Investments	2	2
Accounts Receivable - Net	743	721
Receivable from Affiliates	(3,519)	(3,508)
Materials and Supplies	0	0
Other Current Assets	11	16
Total Current Assets	(2,753)	(2,752)
Properties	2,728	2,708
Accumulated Depreciation	(1,477)	(1,442)
Properties - Net	1,251	1,266
Other Long-term Assets	(281)	(291)
Total Assets	(25,355)	(25,101)
Current Liabilities:
Accounts Payable	29	33
Labor and Fringe Benefits Payable	28	65
Payable to Affiliates	(3,953)	(3,957)
Casualty, Environmental and Other Reserves	12	13
Current Maturities of Long-term Debt	(1)	(1)
Income and Other Taxes Payable	21	16
Other Current Liabilities	9	2
Total Current Liabilities	(3,855)	(3,829)
Casualty, Environmental and Other Reserves	49	51
Long-term Debt	0	0
Deferred Income Taxes - Net	263	258
Other Long-term Liabilities	(325)	(330)
Total Liabilities	(3,868)	(3,850)
Shareholders' Equity
Common Stock, $1 Par Value	(181)	(181)
Other Capital	(5,095)	(5,095)
Retained Earnings	(16,232)	(15,994)
Accumulated Other Comprehensive Loss	21	19
Noncontrolling Interest	0	0
Total Shareholders' Equity	(21,487)	(21,251)
Total Liabilities and Shareholders' Equity	(25,355)	(25,101)
Eliminations and Other | Investments in Conrail
Current Assets:
Investment in Affiliates and Other Companies	847	840
Eliminations and Other | Affiliates and Other Companies
Current Assets:
Investment in Affiliates and Other Companies	15	15
Eliminations and Other | Investments in Consolidated Subsidiaries
Current Assets:
Investment in Affiliates and Other Companies	$ (24,434)	$ (24,179)